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Home >> GMC >> 2018 >> Acadia Denali, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 271 (Lighting System - DTC B0655 To DTC B3890) >> Diagnostic Information and Procedures >> DTC B2625: Display Dimming Pulse Width Modulation Output >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2017 Cadillac ATS. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the harness connectors at the components listed below.
    • S48A Multifunction Switch - Instrument Panel
    • S13D Door Lock Switch - Driver
    • S13P Door Lock Switch - Passenger
  2. Ignition ON, place the S36 Instrument Panel Dimmer Switch in the HIGH position for high backlighting intensity.
    3. NOTE:

    The test lamp in the following step will illuminate at LOW intensity. This is normal circuit operation and does not indicate a circuit malfunction.

  3. Verify a test lamp illuminates between each control circuit terminal listed below and ground.
    • S48A Multifunction Switch - Instrument Panel terminal 3 (with KL9/TR6/UV6)
    • S48A Multifunction Switch - Instrument Panel terminal 4 (without KL9/TR6/UV6)
    • S13D Door Lock Switch - Driver terminal 5
    • S13P Door Lock Switch - Passenger terminal 5
    • If the test lamp does not illuminate 
    1. Ignition OFF, disconnect the X1 harness connector at the K9 Body Control Module.
    2. Test for infinite resistance between the control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K9 Body Control Module.
    • If the test lamp illuminates 
  4. Place the S36 Instrument Panel Dimmer Switch in the LOW position for low backlighting intensity.
  5. Verify a test lamp does not illuminate at FULL intensity between each control circuit terminal listed below and ground.
    • S48A Multifunction Switch - Instrument Panel terminal 3 (with KL9/TR6/UV6)
    • S48A Multifunction Switch - Instrument Panel terminal 4 (without KL9/TR6/UV6)
    • S13D Door Lock Switch - Driver terminal 5
    • S13P Door Lock Switch - Passenger terminal 5
    • If the test lamp illuminates at full intensity 
    1. Ignition OFF, disconnect the X1 harness connector at the K9 Body Control Module, ignition ON.
    2. Test for less than 1 V between the control circuit terminal and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K9 Body Control Module.
    • If the test lamp does not illuminate at full intensity 
  6. Test or replace the component with the inoperative LED backlighting.
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